Vesicant



Patented July 22, 1952 VES ICANT Rudolph Macy, Baltimore, Md., and Benjamin L. Harris and John W. Eastes', United States Army, assignors to the United States. of 'America as represented by the Secretary of War No Drawing.

Application November 29, 1944, A Serial No. 565,784

13 Claims. (01.167 47) (Granted under the act of March 3, 1883, as

The invention described herein may be manufactured and used by the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates, generally, to thickened chemical warfare vesicants, and has particular relation to thickened chemical warfare vesicants particularly adapted to be sprayed from airplanes soas to fall upon the ground in the form of drops.

The important chemical warfare vesicants are mustard (dichlorethyl sulfide), lewisite (chlorvinyldichlorarsine), and the so called nitrogen mustards (tris-[B-chloroethyllamine and ethyl bis-[B-chloroethyllamine). Of these three, mustard is the most important. For certain tactical purposes, it is necessary to spray these vesicants from airplanes. Heretofore', the effectivenessof the vesicants, whensprayed from air-, planes, has been considerably less than the maximum effectiveness obtainable, because,-before the vesicant material reached the earth, a large proportion of it was broken up into a very fine mist and a correspondingly smaller fraction reached the earth in the form of large drops. The higher the altitude of the plane and the higher the airplane speed, the greater was the fineness of the mist which resulted.

Chemical warfare vesicants, when acting in liquid form, are most effective against personnel and materiel when in the form of fairly large drops. As the vesicants change from the drop form into a mist and finally into the vapor phase, they have decreasing vesicant penetrating action through protecting clothing and a smaller amount of protection is required against them.

Heretofore, a high percentage of proper sized drops in a vesicant spray from an airplane could only be obtained at a low altitude ('75-500 ft.) and at a low air speed.

Another very important obstacle heretofore encountered in spraying vesicants from airplanes, with resultant vesicant mist formation, was that the mist could not be aimed to fall on a target with any degree of accuracy. Only the portion of the vesicant in relatively large drop form could be accurately aimed.

Although the dissemination of the vesicants by airplane spray has been specifically considered above, the same general principles also apply to dissemination of vesicants from artillery shell. That is, the greater the explosive charge in the shell, the greater is the dispersion of the vesicant that results.

According -to this invention, it has been disamended April 30, 19281370 0. G. 757) covered that certain polymeric materials can be combined with the recognized vesicants so that thetendency for them to break up into fine mists when disseminated from an airplane or shell is greatly reduced, thereby making it possible to spray the vesicants from relatively high altitudes and at relatively high plane speeds and have the vesicants fall upon the ground in the form of relatively large drops.

Accordingly, the object of this invention, generally stated, is to alter the dissemination properties of chemical warfare vesicants by the addition thereto of certain polymeric materials whereby the altered, vesicants may be disseminated from airplane and shell with a large proportion of the resulting spray being constituted of the vesicant in the form of *drops. Vesicant material, altered in ,this manner, is referred to by those skilled in. the art as thickened vesicants.

A very important object of the invention is the provision of vesicants which can be aimed upon a target with accuracy from the air.

.A.more specific object of the invention is to provide thickened vesicants which are sufiiciently stable to meet military requirements and which require only readily available, non-strategic ingredients for their preparation.

Another object of the invention is to provide thickened vesicants which can be readily prepared in the field with a minimum of equipment and trained personnel.

Other objects of the-invention will, in part, be obvious and will appear hereinafter.

For a more complete understanding of the nature and scope of this invention, reference may be had to the following detailed description, thereof, wherein certain presently preferred examples are set forth and methods of preparation thereof are described.

Briefly stated, it has been found that thickened vesicants meeting military requirements may be prepared by thoroughly and evenly mixing with a vesicant material, such as mustard or lewisite, certain relatively high molecular weight polymers.

A: Although a number of commonly available polying from the industrial applications of the poly- 65: mers.

For example, a large amount of scrap 3 Plexiglas and Lucite is available in the form of sawdust, drillings, and sheet from the various aircraft manufactures.

Although the thickened vesicant compositions may be prepared by blending the thickening polymers with the vesicant agents, the preparation of the compositions may be made considerably more convenient by the use of co-solvents. Of course, when a co-solvent is employed, the thinning action thereof frequently makes it necessary to employ a greater proportion of the thickening material in order to obtain the required viscosity. Various volatile co-solvents may be used such as benzene, chlorobenzene, chlorpicrin, acetone, ethylacetate, nitromethane and nitropropane. The last four mentioned co-solvents are particularly adapted for dissolving cellulose acetate butyrate polymer, while benzene and chlorobenzene are particularly useful when methyl methacrylate and polystyrene polymers are employed.

The various techniques by which the thickened vesicants may, be prepared are illustrated hereinafter inconnection with specific examples. In general, in order to meet requirements for spraying from airplanes, a thickened vesicant should have a viscosity of from 0.3 poise to about 6 poise at 10 C. When no co-solventis used, the desired amount of vesicant is weighed into a mixing vessel equipped with a stirrer, and with the stirrer in operation, the polymer or resin is slowly added. Agitation is continued until the resulting solution becomes homogeneous. The weight of a given batch that can be prepared will depend upon the capacity of the mixer available. When a cosolvent is employed, ordinarily, the desired quantity of the polymer is slowly added to the cosolyent so as to avoid l mping. After stirring the combination for a 'period, the vesicant is added to, complete the mixture. In some cases it is desirable to change the procedure by first forming a mixture of the co-solvent and vesicant, and then stirring the polymer there-into. The most rapid method of thickening developed has been a procedure wherein the viscolizing polymer is first dissolved in a portion of the total Levinstein mustardtogether with all of the co-solvent. When solution of the polymeris practically complete, the remainder of the mustard is added. To some extent, the physical properties of the resultant product in any case depend upon the particular method of preparation thereof.

The following commercial polymers have been successfully used as vesicant thickening agents:

a. Polymethylmethacrylate, 11-2024, from Du Pont production and having a molecular weight of from 40,000 to 50,000.

b. Polymethylmethacrylate, N'DR-169, experimental batch prepared by Du Font and having a molecular weight of about 500,000.

0. Polymethylmethacrylate, NDR-359, experimental batch prepared by Du Pont and having a molecular weight of about 450,000;

a. Polystyrene, Styron CA2-K27, made by Dow Chemical Company.

e. Polyvinyl acetate, Gelva V-45, of the lower molecular weight group (30,000 to 50,000), made by Shawinigan Chemicals Co. Ltd. of Canada.

1. Polyvinyl acetate and polyvinyl chloride copolymer, Vinylite VYHI-I, made by Carbon and Carbide Chemicals Corp.

9'. Cellulose acetate butyrate, made by Tennessee Eastman Corp.

h. Formvar, an acetal of polyvinyl alcohol and formaldehyde, made by Du Pont.

i. 'Durite 8-2560, a'methyl methacrylate polypoise (at 10C.) solutions in a little over one hour with a combined concentration of 15-20% for the resin and co-solvent.

The polyvinyl acetate product known as Gelva V- lfi can be dissolved in from 3 to 4 hours in Levinstein mustard at 30 C., when chlorobenzene is used as the co-solvent. The combined concentration of resin and co-solvent required is about 15-20%- The co-polymer of polyvinyl acetate and polyvinyl chloride known commercially as Vinylite VYHH requires an excessive amount of co-solvent to .go into the solution in mustard, and its thickening power is thereby materially reduced.

The cellulose acetate butyrate resin is not as soluble in chlorobenzene as the other resins tested. However, it is known to be soluble in acetone, nitrometliane and nitropropane." Solution in mustard requires about three hours at 30 C. when this resin is premixed with about three times its weight of nitromethane. It is probable that 6 poise (at 10 C.) solutions can be obtained with a combined concentration of resin and cosolvent of 15%.

The rates of solution, of course, depend upon the particular type of vesicant used as a solvent, and, considering one type of vesicant, depend upon the purity and method of manufacture thereof. For example, rates of solution obtained with Levinstein mustard, do not necessarily hold for purer grades of this vesicant. Styron dissolves in Levinstein mustard and in pure mustard without a co-solvent. In this same connection, the 11-2024 grade of methyl methacrylate polymer gives a 6 poise (at 10 C.) solution in lewisite in about three hours at room temperature, but in a mustard-lewisite mixture requires about 24 hours. Styron also dissolves quite rapidly in lewisite to give a 6 poise solution in about one hour at room temperature.

The fol owing specific formulations have been prepared and have been found to be satisfactory to varying degrees upon being tested:

Example 1 Per cent Durite 8-2560 8 Chlorobenzene l0 Levinstein 82 This solution had a viscosity of 4.09 stokes at 10 0.

, Levinstein mustard 83.5-94

Example 5 Per cent Methyl methacrylate NDR-359 1-1.22 Chlorobenzene 5-10 Levinstein mustard 89-93.7

Example 6 Per cent Polyvinyl acetate, Gelva V-45 5.4-7.5 Chlorobenzene 7.5-16 Levinstein mustard 78.6-85

Example 7 'Per cent Polyvinyl acetate, Gelva V-45 7.5 Lewisite 54.4 Levinstein mustard 38.1

,Example 8 Per cent Vinylite VYHH Chlorobenzene Levinstein mustard 65 Example 9 Per cent Polystyrene, Styron 6 Chlorobenzene 12 Levinstein mustard 82 Example 10 Per cent Cellulose acetate butyrate 5 Nitromethane 10 Levinstein mustard Example 11 Per cent Cellulose acetate butyrate 1 5.0 Acetone 15.0 Levinstein mustard 80.0

Example 13 Per cent Methyl methacrylate, P-l 4.4-7.5 Benzene 13.24-22.5 Levinstein mustard 70.0-82.3

Example 14 Per cent 7 Methyl methacrylate, P-1 7.5 Benzene 22.5 Mustard (thiodiglycol) 70.0

Example 15' Per cent Polystyrene, Styron 5.56-7.5 Benzene 16.67-22.53 Levinstein mustard 70.0-77.8

Example 16 I 7 Per cent Polyvinyl acetate (Du Pont) 5.46-9.23 Benzene l2.'72-22.5 Levinstein mustard 59.2-81.8

Example 17 Per cent Methyl methacrylate, Plexiglas or Lucite 0.48-0.91

Benzene 9.1-1'7.3 Levinstein mustard 81.8-90.4

The compositions of Examples 13 through 17 are adapted to field mixing. In practice, the polymer is first mixed with the solvent, and as need arises, the vesicant is blended into the solvent-polymer mix in the field.

Example 18 Into 497 parts of Levinstein mustard is stirred at room temperature 3.25 parts of a methyl methacrylate polymer having an average molecular weight of about 440,000. (Prepared by polymerizing methyl methacrylate monomer in aqueous emulsion in the presence of sodium cetyl sulfonate emulsifying agent and ammonium persulfate catalyst. Ground Lucite sheet may also be used.) A clear solution having a viscosity of 0.9 poise at 10 C. is obtained by agitating the mixture (tumbling or stirring) from three to six hours at 35 C.

In simulated mortar firing tests, this thickenedsolution breaks up into drops, 29% of which are smaller than 1.5 mm., 53% of which are between 1.5 and 5 mm., and 18% of which are larger than 5 mm.

Compositions having the advantage of somewhat greater speed of solution and better stability are made by stirring the polymeric thickener into mustard containing up to 5% of a co-solvent for the polymer and the mustard, such as benzene or chlorobenzene, or into a mixture of all the co-solvent with part of mustard, the remainder of the mustard then being added.

Example 19 Into 987.3 parts of a mixture of equal parts by weight of Levinstein mustard and benzene is stirred 12.6 parts of methyl methacrylate polymer having an average molecular weight of about 230,000 (prepared in the same manner as outlined in Example 18). Within three hours of agitation at room temperature there is obtained a clear solution having a viscosity of 1.06 poise at 10 C. and a freezing point of 16 C. In firing tests, this solution breaks up into drops of which are between 1 and 7 mm. in diameter, and 40% of which'are between 1.5 and 5 mm. in diameter.

A composition having a very low freezing point (21 C.) is prepared by dissolving 1.05 parts of the same methyl methacrylate polymer in a mixture-of 104.27 parts of Levinstein mustard and 44.68 parts ofv benzene. The resulting solu tion has a viscosity of 0.716 poise at 10 C. 'In mortar firing tests, 90% of the drops are between- 1.5 and 7 mm. in diameter and 30% are between 1.5 and 5 mm.

Example 20 Per cent Nitrogen mustard 99.5 Lucite 0.5

Viscosity=0.65 poise at-10.0 C.

Example 21 Levinstein mustard 49.8 Nitrogen mustard 49.8 Lucite 0.4

Viscosity=0.42 poise at C.

Example 22 Pure mustard 1-; 49.75 Nitrogen mustard 49.74 Lucite 0.50 Viscosity=0.48 poise at 10.0 c.

. Example 23 7 Pure mustard 99.5 Lucite Z 0.5-

Viscosity=0.39 poise at 100 C.

Example 24 Levinstein mustard 98.1.4 Coal tar base 1.4

Lucite Viscosity=0.50 poise at 10.0" C.

Viscosity:0.48 poise at 100 C. field mixing.

Sufficient research and developmentwork has been done to indicate the-following generalizations regarding the invention:

1. Polymeric materials of a molecular weight less than about 30,000 at a'concentra'tion of less than about are less useful than polymers of high molecular weight. .Polymers usefulfor vesicant thickening shouldhave a fairly high rate of solution, a fairly high viscosity/concentration coefiicient, and a low viscosity/temperature coefficient. I I V v 2. Polymeric materials having molecular weights of 150,000 andabove, have high viscosity/concentration coeflicients. That is, for small changes of concentration large changes in viscosity are produced, 7 s

3. The higher the molecular-weight of the polymer, the greater is its thickening ability for vesicants. That is, smaller amounts ofhigh molecular weight polymers are required to produce a given viscosity than ar required of lower molecular Weight polymers. 7

l. Increase in concentration of a given polymer results in more or less proportionate increase in viscosity or thickening of a vesicant.

5. The vesicant properties of the vesicants are notimpaired'and freezing points and vapor pressures areessentially unchanged by the polymeric thickeners.

. 6. Temperature and particle size affect the rate of solution of the various viscolizing polymers; higher temperatures'and increased particle fineness both resulting in increased rates of solution. Field thickening can be accomplished by using no more equipment than an open-head drum and a wood paddle for mixing the solutions. Of course, an inclosedmixer provided with some type of power driven agitator is more convenient if available. The following solutions are suitable f r field thickening by addition to mustard:

a. or polyvinyl acetate in benzene.

b. 25% celluloseacetate butyrate in acetone.

0. 5% scrap Plexiglas or Lucite in benzene.

d. 25% Styron in benzene. v

In addition to the foregoing, it has been found that Levinstein mustard may be thickened with a viscous solution of polymers in either lewisite or pure mustard. A viscous solution of methyl methacrylate polymer in pure mustard serves very well for this purpose. For example, a solution composed of about 23% methyl methacrylate polymer (Plexiglas or Lucite) about 10% nitrogen bases, and about 87-88% pure mustard, has been found to be a satisfactory field thickener for Levinstein mustard for airplane spray. The use of pure mustard as a solvent for the polymer has the obvious advantage over the use of other solvents, such as benzene, in that it gives an airplane spray having as great as or greater mustard content than the unthickened Levinstein mustard.

thickened It should also be mentioned that interpolymers, such as those of styrene with acrylates or methacrylates, may be used for thickening purposes.

Although the function of the polymers com bined withthe vesicantshas been referred to above as a thickening action, and the resulting products have been referred to as thickened vesicants, this terminology has been used in a scope thereof.

general sense in th absence of more accurate terms. As a matter of fact,'it has been found that the problem of obtaining vesicants, which upon being sprayed form a large percentage of drops is considerably complicated and is not entirely a matter of increasing viscosity.

Levinstein mustard referred 'to above is,in'- tended to designate'that grade of product obtained from the Levinsteinmustard gas manufacturing process. This grade of mustard is a relatively impure form, the. mustard content being about When freshly made, Levinstein H is a solvent for th various polymeric thick eners. However, when it ages, as in normal storage, it undergoes changes, such as'increasing in iron content, which renders it incapable of dissolving certain polymers, particularly methyl methacrylate. This lack of solubilitylcen beovercome by the use of sufficient 30% or more) amounts of co-solvents, such'as lewisite or pure mustard. Furthermore, it has been found that the addition of certain nitrogen bases (coal tar bases, peroleum bases, etc.) to Levinstein H in concentrations of about 2% completely overcomes thls lack of solubility of methyl methacrylate polymer. A favorite means of adding the nitrogen bases in field thickening operations is to have the benzene or pure mustard solution of methyl methacrylate polymer contain about 10% of the nitrogen base.

A pure grade of mustard containing mustard is obtained from the thiodiglycol process of manufacturing mustard or by purifying Levinstein mustard as by distillation All percentages referred to in the foregoing description and in the appended-claims are percents by weight.

The molecular weights given above for the various polymers, are based on viscosity measurements and are sometimes referred to as Staudinger molecular weights.

It will be understood by those skilled in the art that the foregoing illustrative formulations and techniques of preparation are illustrative of the invention, and that a number of other compositions may be prepared which come within the Accordingly, all material described above is intended to be by way of illustration and not by way of limitation.

1. A new composition of matter consisting of a liquid having a viscosity of from 0.3 poise to 6.0 poise at 10 0., the characteristic of forming fairly large liquid drops when sprayed'into the air, and comprising at least one chemical warfare vesicant selected from the group consisting of Levinstein mustard, nitrogen mustards, pure mustards and lewisite, thickened with not in excess of about 10% by weight of a polymer having a molecular weight of at least about 30,000.

2. A thickened vesicant consisting of a liquid having a viscosity of from 0.3 poise to 6.0 poise at 10 C., the characteristic of forming fairly large liquid drops when sprayed into the air, and comprising at least one chemical warfare vesicant selected from the group consisting of Levinstein mustard, nitrogen mustards, pure mustards, and

9 lewisite, thickened with polymethyl-methacrylate.

3. A thickened vesicant consisting of a liquid having a viscosity of from 0.3 poise to 6.0 poise at 10 C., the characteristic of forming fairly large liquid drops when sprayed into the air, and comprising at least one chemical warfare vesicant selected from the group consisting of Levinstein mustard, nitrogen mustards, pure mustards, and lewisite, thickened with polystyrene.

4. A thickened vesicant consisting of a liquid having a viscosity of 0.3 poise to 6.0 poise at 10 C., the characteristic of forming fairly large liquid drops when sprayed into the air, and comprising mustard thickened with methylmethacrylate polymer and a co-solvent for the mustard and polymer.

5. A thickened vesicant consisting of a liquid having a viscosity of 0.3 poise to 6.0 poise at 10 C., the characteristic of forming fairly large liquid drops When sprayed into the air, and comprising from about 76 to 91.2% of Levinstein mustard from about 4.0 to 8.0% of methyl methacrylate polymer, having a molecular weight of 40,000 to 50,000 and from about to 16% of chlorobenzene.

6. A thickened vesicant consisting of a liquid having a viscosity of 0.3 poise to 6.0 poise at 0., the characteristic of forming fairly large liquid drops when sprayed into the air, and comprising from about 70 to 77.8% of Levinstein mustard, from about 5.56 to- 7.5% of polystyrene polymer, and from about 16.67 to 22.5% of benzene.

7. A thickened vesicant consisting of a liquid having the characteristic of forming fairly large liquid drops when sprayed into the air, and comprising about 99.5% of nitrogen mustard and about 0.5% of methyl methacrylate polymer, and having a viscosity of about 0.65 poise at 10 C.

8. A thickened vesicant consisting of a liquid having the characteristic of forming fairly large liquid drops when sprayed into the air, and comprising about 99.6% of Levinstein mustard and nitrogen mustard in substantially equal proportions, and about 0.4% of methyl methacrylate polymer, and having a viscosity of about 0.42 poise at 10 C.

9. A thickened vesicant consisting of a liquid having the characteristic of forming fairly large liquid drops when sprayed into the air, and com- 10 prising about 99.5% of pure mustard and nitrogen mustard in substantially equal proportions and about 0.4% of methyl methacrylate polymer, and having a viscosity of about 0.48% poise at 10 C.

10. A thickened vesicant consisting of a liquid having the characteristic of forming fairly large liquid drops when sprayed into the air, and comprising about 99.5% of pure mustard and about 0.5% of methyl methacrylate polymer, and having a viscosity of about 0.39 poise at 10 C.

11. A thickened vesicant consisting of a liquid having the characteristic of forming fairly large liquid drops when sprayed into the air, and comprising about 98.1 of Levinstein mustard, about 1.4% coal tar base, and about 0.5% of methyl methacrylate polymer, and having a viscosity of about 0.50 poise at 10 C.

12. A thickened vesicant consisting of a liquid having the characteristic of forming fairly large liquid drops when sprayed into the air, and comprising about 70.0% of Levinstein mustard, about 29.7% of lewisite, and about 0.3% of methyl methacrylate polymer, and having a viscosity of about 0.4 poise at 10 C. after field mixing,

13. A thickened vesicant consisting of a liquid having the characteristic of forming fairly large liquid drops when sprayed into the air, and comprising about 80.0% of Levinstein mustard, about 17.6% of pure mustard, about 2.0% coal tar base, and about 0.4% of methyl methacrylate polymer, and having a viscosity of about 0.4 poise at 10 C. after field mixing.

RUDOLPH MACY. BENJAMIN L. HARRIS. JOHN W. EASTES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,620,475 Lawrence Mar. 8, 1927 FOREIGN PATENTS Number Country Date 559,359 Germany Sept. 19, 1932 

1. A NEW COMPOSITION OF MATTER CONSISTING OF A LIQUID HAVING A VISCOSITY OF FROM 0.3 POISE TO 6.0 POISE AT 10* C., THE CHARACTERISTIC OF FORMING FAIRLY LARGE LIQUID DROPS WHEN SPRAYED INTO THE AIR, AND COMPRISING AT LEAST ONE CHEMICAL WARFARE VESICANT SELECTED FROM THE GROUP CONSISTING OF LEVINSTEIN MUSTARD, NITROGEN MUSTARDS, PURE MUSTARDS AND LEWISITE, THICKENED WITH NOT IN EXCESS OF ABOUT 10% BY WEIGHT OF A POLYMER HAVING A MOLECULAR WEIGHT OF AT LEAST ABOUT 30,000. 